Loop bin duplicator

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A loop bin duplicator is a specialized audio tape machine used in the duplication of pre-recorded audio cassettes.

Magnefax 7in duplicator

Analog Loop Bin Duplicator[edit]

An analog loop bin uses a long loop of 1/2" wide tape loaded in a large bin located in the front of the machine, which is read on both sides by the duplicator at a very high speed, either 32, 64, 80, or 100 times the normal speed of playback (1.875 ips) of an audio cassette (60, 120, 150, and 187.5 ips respectively).

While this loop is being played back, the audio signals for the A and B side are sent to a "slave" recorder or an audio bus that contains multiple "slaves". The "slave" records the A and B side to a reel of raw 1/8" audio tape wound on a "pancake" reel (similar to motion picture film wound on a plastic core) at the same high speed. After it is recorded, this pancake of tape is then loaded onto special machines called loaders. The loader has cassette shells containing only a leader called C-0 cassettes that are loaded one at a time or into a hopper where the C-0s are fed automatically depending on the type of loader. The tape from the pancake is then spliced onto the C-0 cassette's leader and then wound into the cassette by the loader.

The 1/2" loop of tape in the duplicator usually will have a segment of clear leader spliced in between the beginning and end of the program (with some duplicators using a metal foil splice instead). This clear leader splice is read by an optical sensor (or in the case of a foil splice, coming in contact with electrical contacts in the tape path) in the loop bin duplicator, which triggers a cue tone that is recorded to the reel of 1/8" pancake tape. This cue tone tells the loader to stop and cut the tape from the pancake and splice it to the other length of leader in the cassette shell (a process called "de-spooling"). In fact, part of this de-spooling tone can be heard at the leader splice of some previously recorded audio cassettes, as a very low-frequency arpeggiated rumbling, but as an actual tone when played back at a higher speed.

In the XDR duplication process, the loop bin duplicators use 1"-wide loop tape instead, yielding in a better quality duplication.

Digital loop bin duplicator[edit]

Digital loop bins were also introduced in the early 1990s. The early digital loop bins replaced the source tape with audio data stored on hard drives that was read and sent to digital-to-analog converters that were connected to the "slave" recorders, but they were prone to failure because of the amount of stress put on the hard disks.

The hard disks were replaced by huge RAM buffers which eliminated the failures but added greatly to the expense of the equipment. Since a digital bin was capable of playback speeds of 256:1 or better, a single bin could perform as two by splitting the buffer between two different programs. A program could be loaded and looped for production while an additional program could be loaded into the buffer. A real-time monitoring system could play back the audio stored in either buffer to check for potential flaws in the audio while both programs were looping for production.

Another difficulty to overcome was the means for loading a digital bin. A bin could be loaded manually by recording directly into the bin's buffer, or it could be loaded by a high speed data device. At the time digital bins were first put into production, an S-VHS based storage device manufactured by Honeywell called a VLDS (Very Large Data Store) was used. A single S-VHS tape was capable of storing over 5 GB of data. These extremely expensive storage devices were eventually replaced by CD loading.

The benefits of using a digital loop bin are:

  • There is no master tape to degrade during the copying process
  • Only a single master has to be made
  • Audio can be transferred at a much higher rate
  • The audio being reproduced can be monitored during production without shutting down the bin
  • Eliminates tape hiss from the source tape

The disadvantages:

  • Initial cost
  • Flaws in a recording would result in loud pops and cracks rather than a more subtle analog degradation.
  • Generated a lot of heat and could start to overheat if not properly air-conditioned.

External links[edit]